Charles l



(NS Model.) S 4 0. L. BUQKINGHAMF DUPLEX TELEGRAPH.

No. 258,366.. Patented May 23. 1882.

' WITNESSES:

INVENTOR &4, KL. BY 3/171! ATTORNEY Unrrnn STATHs PATE T Uterine.

cHARLEs L. BUOKINGHAM, on ELIZABETH, NEW JERsEY, ASSIGNOR To THE wEsTERn UNION TELEGRAPH COMPANY, OF NEW YORK, N. Y.

DUPLEX TEl EGRAPH.

SPECIFICATION forming part of Letters Patent No. 258,366, dated May 23,1882.

Application filed June 16, 1881.

1'0 all whom it may concern Be it known that I, OHARLEs L. BUCKING- HAM, of Elizabeth, county of Union, and State of New Jersey, have invented anew and useful Improvement in Telegraphy, of which the following is a description, reference being bad to the accompanying drawings, forming a part hereof.

My invention is applicable to differential systems of telegraphy for the simultaneous transmission of messages upon a single line in opposite directions, and has for its special object the neutralization in the receiving-instruments of duplex, quadruplex, orsextuplex telegraphy of-disturbing effects due to static induction upon the main line; and to this endI employ at each station a norm all y-closed bridge or branch conductor to join the main'and artificial lines. The bridge or branch conductor is normallyclosed through a contact-point and the armature of an electro-magnet, and the position of said armature, whether to open or close the bridge, depends upon the currents which are transmitted by the keys of the home and'distant stations. When only signals are being sent from the home station the bridge 'remains closed, and from this fact equal strengths of current will flow through the two oppositely-wound coils of the home receivingrelay both while the main line is receiving its inductive charge and thereafter, during the continuance of a signal and after the main line has received its full inductive charge.

It is well understoodin the art of duplex tclegraphy that in a' differential duplex while the main line is receivingits inductive charge a stronger current will flow through the mainline coil than through the oppositely-wound coil in theartificial circuit, and that the dilferential receiving-relay will respond to give a. false signal. The bridge, however, which I employ effects a complete balance of currents sent through them from the home station. Following each signal that is sentfrom the home station is aquick static or inductive discharge fromthemain line in a direction opposite to that of the current of charge. The direction of the current of inductive discharge is such as to tend to causethe bridge to be broken.

However, the armature of the bridge is soad- (No model.)

justed that the bridge will practically remain unbroken from the effects of such inductive discharge, and it will distribute itself inpassing to earth equally through the two oppo sitely-wonnd coils of the receiving-relay, and nofalse signal will follow. While the bridge will not be broken by a quick inductive discharge from the main line, a battery-current sent from a distant station sufficiently prolonged to produce a signal at the home station will cause the bridge to be opened and remain open during the signal, wherefore the current willonly pass through one coil of the home receivingrelay and a signal will be given. By this means the main-line inductive charge and discharge produce neutral efiects upon receivingrelays when signals are sent from the same stations, and this end is accomplished Without the necessity of adjustment to change the elec- 'tro-static capacity of an artificial line to bal- 7o ance the highly-variable inductive efiects of the main line.

I will now explain my invention by reference to the accompanying drawings.

Figure 1 represents an ordinary dupleX'system in which the bridge at each station is broken by means of an ordinary differential OlGClIOHIHgHGlJ whose coils are in the main and artificiallines, respectively. Fig. 2 shows a modified means forbreaking the bridge-con- 8o ductor, which consists of a polarized rela whose coil is in the main line alone. i

In Fig. 1, A and B represent two distant stations, joined by a main line, L.

M and M are two 1nain-line batteries, ar-

ranged to oppose each other when simultaneously connected to line. In all' other respects the devices of station 13 are identical with those of station A, and a description of apparatus-of one station will suffice for that of both.

R is an ordinary differential receiving-relay, having oppositely-wound coils a: and y, formin gparts respectively of the main and artificial circuits, and c is its armature-tongue.

K is an ordinary continuity-preserving key.

T is a resistance placed in the artificialcircuit equal in amount to the main-line resistance. The artificial line is connected to earth at E S is a differential electro-magnet altogether similar in general respects to relay R,its coils z and to being oppositely wound and forming parts of the main and artificial lines.

2 and 3 are pointsin the main and artificial lines,joined with a bridge or branch conductor of very low resistance, which is normally closed through armature a and stop I).

r is a small rheostat for establishing a proper proportion of resistances of cond uctors between points 1 and 2 and 1 and 3. Q

When Kis depressed the currentof battery M divides at point 1,one portion passing through coils w and z and the other through coils 'y and w of the relay B and electro-magnet S. When the two portions of the current thus divided are equal the electromagnetic effects of 00 and y are neutral, also those of z and w but owing to'the greater capacity of the main than the artificial-line for a static charge the current fromM at the beginning of each signal, if there be no compensating device, will betstrongerthrough coils a: and z of the main line than through coils y and wof the artificial-circuit. However, it points 2 and?) be connected by a bridge which is normally closed, it is obvious that until such bridge is broken the current flowing through coil to must equal that passing through y, even if the current which-flows to the main line from point 2 is much greater than that; flowing over the artificial line from point 3 to E Primarily, therefore, owing to the normally-closed bridge joining points 2 and 3, the current ofM willbe divided equally through the coils x and 3 but while the bridge causes an equal division of current between coils a and y, more current at the same time will flow through coil 2 than 10, whereby S will become magnetic and tend to attract its armature. However, if S be slightly sluggish and armature a. properly adjusted, the bridge will notbe broken until the main line will have received its inductive charge. After the line has received its inductive charge the current from M will divide itself at 1 equally, and it will be immaterial ifthe bridge be momentarilybroken.

When the resistance of the bridge compared with that of either or or 3 is practically zero, and resistances of a: and y are equal, it will be observed that at the moment of charging the main line, when more current is flowing into said main line than to the artificial circuit, a current will be set up in the bridge from 3 toward 2, and that the division of current at point 1 will be equal through or and 3 The removal of battery M after sending each signal is accompanied by a static discharge opposite in direction to the corresponding current of charge. The current ofstatic discharge which would otherwisepass through only coil .1: of the difierential relay R divides equally at point 2, one portion passing to earth by coil '31 and the other by the oppositely-wound coil w, whereby the effects of static discharge are neutral upon the receiving-relay. As the static discharge from the line passes through only one coil of S, it will tend to break the bridge; but by a proper construction of S and adjustment of a thebridge will not be broken before a complete discharge can occur. While the static dischargeof the main line is not sufiicient to cause the bridge to be broken, a sufficientlyprolonged current i'rom a distant station to makea telegraphic character will attract armature a and retain it. during the time of the signal, and the current will thereby pass wholly through coil m to effect a signal. If the batteries M and M arelboth simultaneously upon the line, and battery M be then removed, the accompanyingstatic discharge will not neutralize itself by passing through both coils m and y, as the bridge is broken when both batteries are to line, and so remains when M is removed. The static discharge under this condition discharges wholly through x; but this will produce nofalse' signal by attracting c,--as c is already attracted from theagency of the closed key at the distant station. The static discharge will therefore only conspire to hold a inits proper position. 1 I will now describe my modification illustrated in Fig. 2. S isa relay having a polarized core and a polarized armature-tongue, a, for the purpose of breaking and closing the bridge-conductor joiuing'points2 and 3, the functions of which are fully set forth in the description of Fig. 1. The coil of S is in the main line, and when no current is flowing through said -coil thepolarized armature a is repelled, as the magnetisms of wand the adjoining end of S are of like polarity-say north. When a current is sent from Mthe armature is more strongly repelled, as the-direction of the current is such as to induce north magnetism in the end of core S facing a,- but when a current is received from a distant station to effect a signal the armature will no longer be repelled; but the magnetism of the core will be reversed, the armature will be attracted, the bridge will be broken, and a signal received. The retractile force of the armature, however, is so adjusted as not to be materially moved by the static discharge from the line, though its direction be the same as a current giving a signal. By means of the polar circuit-breaker the bridge cannot by any possibility be broken when the line is receiving its inductive charge, as its action is wholly indcpendentof the current of the artificial line. However strongand prolonged the effect of static charge, polar armature a will not be moved and equality of current strength in coils m and y will remain unchanged.

1- do not herein claim the combination ateach station ofa main line, an artificial compensatin g-circnit, a receiving-instrument, a bridge or branch conductorvconnecting the main and artificial lines, and an automatic circuit-breaker for opening and closing said bridge, since I shall claim said combination in a separate patent.

WhatI claim, and desire to secure by Letters Patent, is-

1. The method, substantially as specified, of

IIO

causing both the inductive charge and discharge respectively through the receiving-inr 5 strunient at-the transmitting-station to he divided before passing through said receivingrclay, whereby the divided portion will act oppositely thereon to produce neutral effects and avoid false signals.

Executed June 13, 1881.

CHARLES L. BUOKINGHAM.

Witnesses:

J 0s. E. FENN, F. L. FoULKs. 

